For starting internal combustion engines, drives are used that are fed by an energy source that is independent of the fuel supply. DC motors are used, generally whose driving pinions first engage with a toothed rim of the internal combustion engine, in order to actuate the internal combustion engine. At the end of the starting process, the driving pinion disengages again from the toothed rim of the internal combustion engine. In the process, a common relay is used for the engaging process and switching through the main current for driving the DC motor. An associated overview diagram is illustrated in FIG. 1. It shows a relay 1 connected to a terminal 50, a switch 2, a control unit 5, a terminal 30 of the motor vehicle, and a starter motor M. Control unit 5 has a driver TRO having a switching unit T00, which is acted upon by a switching signal S00. When switching unit T00 is switched through, relay 1 is connected via a control line SLO and terminal 50 to a positive operating voltage +. Thereupon relay 1 operates and closes switch 2. Because of the closing of switch 2, starter motor M is connected to terminal 30 of the motor vehicle and thereby put in operation.
A starting device for starting an internal combustion engine is described in European Patent No. EP 0 848 159 B1, which has a starter motor that is able to be connected to a voltage source via a starter relay, and is able to be brought into engagement with the internal combustion engine for cranking it up. Furthermore, an electronic control unit is provided for actuating the starter relay and/or the starter motor. This controls semiconductor power output stages, assigned to the starter relay and/or the starter motor, in such a way that, at least in a start-stop operation of the internal combustion engine, the starter relay has its engaged position in a start-stop condition of the internal combustion engine. In this starting device, the starter relay has current applied to it after the operation of a starter switch, so that, on the one hand, a contact is closed which connects the starter motor to a supply voltage and, on the other hand, independently of that, engages the pinion of the starter motor with a toothed rim that is situated on the crankshaft of the internal combustion engine.
German Patent Application No. DE 10 2009 000 125.5 describes a device for actuating an electromagnetic switching element, particularly a relay, in which the time that elapses between the triggering of the operating and the operating, and also the time that elapses between the triggering of the dropping off and the dropping off, is reduced. Such a relay may be used in connection with pinion starter-based start-stop systems. To actuate such a relay, three control lines are provided via which a control unit actuates switching elements which, as a function of its switching position, permit or block current flow through two coils of the relay that are able to have current applied to them independently of each other.
An increasing spreading in the market for motor vehicles has start-stop functionality, is connected with broadened requirements on the starting system of the motor vehicle, and also with the broadening of the functions. In particular, at each starting requirement by the driver, the starting capability of the vehicle has to be assured. Moreover, it has to be assured that, during starting, no voltage dips occur, or only slight ones. This may be achieved in that the main current for the starter motor is guided via a series resistor, for one, and time-delayed directly to the starter motor, for another. This makes a separation of the functionalities of a usual starter relay necessary. One approach to this is to provide a first relay for engaging the driving pinion, and to use two additional relays in order to guide the main current for the starter motor, for one thing, via a series resistor and, for another thing, time-delayed directly to the DC motor.